The present invention relates to a fluid valve used in a faucet and in particular to such a faucet which utilizes two non-resilient members to regulate the flow of fluid through the faucet.
Present fluid valves used in faucets typically incorporate resilient seals to control and/or shut off the flow of fluid therethrough. Although resilient seals are effective in shutting off the flow of fluid, they have a number of deficiencies. For example, resilient seals wear with use and their resilient properties deteriorate with time due to exposure to the variable temperature fluid medium and the degrading effect thereof. This deterioration results in premature failure of the seal resulting in leaks and a loss in performance.
Another unwanted characteristic of resilient seals is the effect of thermal expansion on valve performance. In valve configurations where the flow rate of the fluid medium is controlled by the flow area regulated by the resilient seal, expansion and contraction of this seal due to fluid thermal variation will affect the flow area, either reducing or increasing the flow depending on the direction of change of the temperature of the fluid medium. This phenomenon when changing from a low to a high temperature is commonly referred to in the plumbing trade as "hot water shut-off" where flow of the water is severely restricted.
Another type of prior art valve is commonly referred to as a shear plate type wherein two plates are used to control the flow of fluid medium and the two relatively movable plates are always in contact with each other. Such continuous contact between the plates creates frictional drag. Also, full contact type shear disc valves have a "dead band" zone resulting from the overlap condition of the openings between the stationary and movable discs.
The valve in accordance with the present invention eliminates the "hot water shut-off" condition common with resilient seal valves because the hard ceramic material forming the non-resilient discs has a low coefficient of expansion. Accordingly, the flow area created by the two discs stays constant over extreme variations in fluid temperatures.
Since the flow area for the fluid is directly proportional to the location of the movable disc relative to the stationery disc, the moment the valve is actuated to move the movable disc, fluid begins to flow through the valve. Prior art valves normally have an inherent "dead band" zone between the extreme mechanical shut-off position and the relative position of the discs of the valve when fluid begins to flow. The advantage of having a zero "dead band" zone is easier user operation since flow is predictable and instantaneous when the movable disc separates from the stationary disc.
It is accordingly an object of the invention to eliminate the deficiencies of the prior art resilient seal and shear plate type valves.